The key physiological cue for migration is definitely the modifications within the day length. These modifications are associated with hormonal improvements within the birds. While in the time period in advance of migration, several birds display greater exercise or Zugunruhe (German: migratory restlessness), 1st described by Johann Friedrich Naumann in https://donovanoyems.qowap.com/96680760/not-known-details-about-getting-a-pet-bird-advice